Sorry to hear the problems you have been having. Utilisation issues are never posted to the Status Pages as they are usually a P4 fault (degraded service). Only faults of P2 and above will be automatically posted. The status page is designed more toward a total loss of service rather than degraded.
Support Staff have access to all known open faults and will check your CMTS/cable against them. If it matches then they will assign a fault ticket on your account with the reference number.
Utilisation issues can take anything from a month or more to be upgraded (depending on the severity)
The engineer is wrong to say
"utilisation shouldn't affect 20mb customers anyway" as this is untrue.
At this stage and the problems you've had, then I think thenry's advice above would be a good idea.
Let us know how you got on
